Superficial micro-mechanically produced MEMS structures having high aspect ratios are generally produced by structuring thick layers, for example, polysilicon layers, by means of a DRIE (dry reactive ionic etching) etching process. However, this procedure has special properties for MEMS components having structural elements which are driven in the plane and suspended via spring elements. Because of the construction of the DRIE etching facilities, the structures no longer have symmetrical cross sections toward the wafer edge, but rather are distorted like parallelograms. As a result, an undesired movement torque out of the plane can arise, which possibly has an effect on the functionality.
For example, the correction, which is required due to the parallelogram-type distortion in rotation rate sensors in the MEMS and ASIC designs, requires a high degree of complexity and chip surface. This is primarily expressed in the so-called quadrature compensation. The quadrature is an error signal which is coupled into the detection by the drive of the rotation rate sensor. This compensation requires providing voltages greater than 10 V, which can only be provided by the ASIC in a manner linked to high costs.
In addition, presently the functional layers frequently consist of polycrystalline silicon layers. The grain sizes are in the order of magnitude of the lateral spring widths in this case, which has the result that individual grains and the crystal orientation thereof can strongly influence the mechanical behavior of individual spring suspensions in the ranges of stress maxima.
Vapor-liquid-solid or vapor-solid-solid methods for selectively growing monocrystalline layers are known, for example, from “Growth, Thermodynamics, and Electrical Properties of Silicon Nanowires”, V. Schmidt, J. V. Wittemann, and U. Gösele in Chem. Ref. 2010, 110, pages 361 to 388 and from “Catalytic Growth of Nanowires: Vapor-Liquid-Solid, Vapor-Solid-Solid, Solution-Liquid-Solid and Solid-Liquid-Solid Growth”, K. W. Kolasinski, Current Opinion in Solid State and Materials Science 10 (2006), pages 182 to 191.